Although the present apparatus is suitable for separating minerals from various solutions or mixtures, it will be described for illustrative purposes in connection with the recovery of salt by evaporation. There are three commonly used salt recovery processes including mining evaporation from solution using artificially generated heat which has become very expensive, and solar evaporation. This invention is of the latter type and is intended to replace in part or whole these prior art processes for recovery of salt or other minerals, especially those using scarce artificial heat sources for evaporative purposes. One prior art approach has been to confine sea water in a large shallow pond, and to harvest the salt after the water has completely evaporated. However, this approach is practical for use only in very arid regions, since in high rainfall areas the partially evaporated level would be frequently diluted. The improvements of this invention solve the latter problem while raising the efficiency of evaporation to a relatively higher rate. Typical prior art evaporative systems are shown in U.S. Pat. Nos. 681,407 to Coward; 737,551 to Blanchard; 1,491,068 to Schilling; and 1,506,946 to Schilling in which the objective is the recovery of salt. Other patents which are more directed toward the distillation and recovery of a liquid include U.S. Pat. Nos. 631,461; 102,633; 2,383,234; 3,167,488 and 3,278,396.
The present invention seeks to optimize the rate of evaporation by using dark-colored surfaces and regulating the sprayed solution so as to provide a thin film of almost zero depth upon the evaporative surface so that the sprayed film is quickly heated throughout its depth, but is thin enough not to unduly cool the surface. Other problems solved in this invention are the shaping of the surface in such a way as to expedite the recovery of salt which is deposited as precipitate on the evaporative surface, and the protection of the process and apparatus from rainfall.